Field
This invention relates generally to a twistlock and, more particularly, to an expanding clamping twistlock that has particular application for engaging an ISO aperture in a fitting, where the twistlock employs a system of screws and cams that secure a structure in both a fore/aft direction and a vertical direction.
Discussion
Massive container ships that are able to transport many shipping container across oceans and between countries generally define worldwide commerce. The shipping containers transported by these ships have a certain size, weight and configuration that are defined by the International Organization for Standardization (ISO). In order to comply with ISO requirements, the shipping containers include a corner fitting securely mounted to each of the eight corners of the container that allows the container to be lifted by a crane using suitable connecting mechanisms, such as hooks, and allow the shipping containers to be secured to the deck of the ship and to each other so that the containers can be stacked on the deck to a height that is often times breath taking. Each of the corner fittings includes specially configured slots or ISO apertures in the faces of the fitting directed outward, where each fitting will include a top or bottom aperture, a front or back aperture and a side aperture. Further, ISO apertures are generally provided at desirable locations in the deck of the ship. Other types of ships, such as various navy ships, also employ various types of fittings that have ISO apertures.
Connectors are required to engage the ISO apertures in the corner fittings or otherwise so as to allow the containers to be secured to each other and to the deck of the ship in a manner that allows the containers to be reliably coupled together in the open sea. These connectors often employ a twistlock design where an engaging portion of the connector is inserted into the ISO aperture and is rotated to engage an underside surface within the fitting to secure the connector to the fitting. Various types of twistlock designs are known in the industry that operate in this manner.
In many of these twistlock designs, the engaging portion of the twistlock has a size that is significantly smaller than the ISO aperture so that there is “play” in all directions after the twistlock is secured to the fitting, and thus, known twistlocks may not provide a tight fit between ISO apertures. For applications where twistlocks are used for securing a structure to the deck of a ship that may not be shipping containers, where multiple twistlocks may be employed to secure the structure, one or a few of the twistlocks may be carrying the entire load in these other directions, providing a recipe for failure. Therefore, it would be desirable to have a twistlock for securing shipping containers or other structures to the deck of a ship that eliminates play and provides a tight fit to evenly spread the load between fittings along all axes.